Seasonal Variations in Total Antioxidant Capacity and Total Phenolics Content of Leaves of Phyllostachys Taxa Using Different Extraction Methods

摘要

Changes in total phenolic content (TP) and total antioxidant capacity (AC) during the vegetation period (April-November) were analysed in Phyllostachys aureosulcata f. aureocaulis (PAA), P. flexuosa (PF), P. humilis (PH), P. sulphurea var. sulphurea (PSS). Different extraction methods were compared: infusion or decoction with water or aqueous methanol. The highest significant value for TP was measured in the case of infusion at 90 ?°C for 5 min, which lead to the highest value for AC. During the vegetation period the highest values of TP were measured in April and May in the case of PAA (409.5; 314.9 and 258.7; 119.0 μg GA/ml) and PH (388.4; 411.6 and 252.9; 253.3 μg GA/ml). There was a clear trend in the changes of TP, with high values in April and November and a peak during August-September. Similar to TP, the highest values of AC were measured in April and May in PH (519.7; 566.3 and 513.5; 510.4 μg AA/ml) and PAA (534.5; 337.8 and 394.9; 275.4 μg AA/ml). We compared the change of TP in all taxa with stress index values derived from daily maximum and minimum air temperature, cumulative precipitation plus irrigation and cumulative evapotranspiration values. A close correlation R2 = 0.32 (p=0.001) was found between stress index values and the change in TP of all taxa. The correlation is even closer R2 = 0.52 (p=0.001) with PF, PH and PSS. Our results with PAA can be explained by possible inter/intra-specific differences in freeze tolerance and cold-acclimation.